Does playback speed affect recording

[lawrencelile]

Does changing the playback speed slider in the toolbar affect recording?

Recently I accidentally hit this slider while recording, thought I set it back to 1.0. I noticed some odd things about the recording later - difficult to sync it with video that was recorded simultaneously. Does the playback speed affect a recording? If I accidentally set playback speed to 99%, then recorded for an hour, would it in fact be 1 hour and 1 minute when played back or something like that? (or maybe 59 minutes or something ...) Awfully hard to get the lips to move when the speaker says something, I'm looking for explanations.

Running Audacity on Win 7, recent download but don't know the exact version.

[Gale Andrews]

Is your main system Ubuntu though? That is what you said when you registered.


Gale

[Gale Andrews]

Does changing the playback speed slider in the toolbar affect recording?

No. But you can't rely on the clock in the built-in sound card. And different sound cards will have different clock speeds, so record from the same device that you want to play back on.



Gale

[steve]

Does changing the playback speed slider in the toolbar affect recording?

No.

If the video and audio were recorded on different devices, it's very likely that they will run at slightly different speeds.
The professional solution is to synchronise all devices to a master clock signal. Consumer level devices do not have this option.

The workaround when using consumer / semi-pro equipment is to give yourself a timing mark at the beginning of the recording, and another at the end (traditionally this would be a "clapper board", but just clapping hand on camera and at the same time on the audio recording, will do the job). You can then look in your video editor to see what the exact required length is between your two "clapper board" points, then use the "Change Speed" effect in audacity to stretch the audio to that exact same length.

recent download but don't know the exact version.

You will find the version number of Audacity in "Help menu > About Audacity".

[lawrencelile]

Does changing the playback speed slider in the toolbar affect recording?

No. But you can't rely on the clock in the built-in sound card. And different sound cards will have different clock speeds, so record from the same device that you want to play back on.



Gale

So this is probably clock slippage between two recorders. I didn't know that was a thing! The longer we record, the worse the slippage gets, and it seems to vary from day to day, some days it is not a problem. Prolly depends on the temperature of one of the devices or something.

The hack I ended up doing was adding slices of time in the audio portion of the edit, typically when the fast-talking lecturer takes a breath, and then re-syncing manually. Ended up having to do this 4-5 times over an hour's lecture. That's tedious. 10 minutes of listening to the same 5 seconds over and over again each time I sync. Can you end up in the nut hatch from this? If we could solve the tech problem of recording video and audio on the same device, this would be a lot easier, but so far niether 3 geeks nor the factory can figure it out. Been on the phone with them for an hour, gave up.

Yeah, the recording computer is using windows although I use linux on other computers.